Core Concepts and Computations in Microeconomics

Definitions and Key Concepts in Microeconomics

Marginal Costs and Marginal Benefits

Marginal cost and marginal benefit are foundational concepts in microeconomics, used to analyze decision-making at the margin.

• Marginal Cost (MC): The additional cost incurred from producing one more unit of a good or service.

• Marginal Benefit (MB): The additional benefit received from consuming one more unit of a good or service.

• Graph Properties: Marginal cost curves typically slope upward due to increasing opportunity costs, while marginal benefit curves often slope downward due to diminishing returns.

Formula:

• $MC = \frac{\Delta TC}{\Delta Q}$

• $MB = \frac{\Delta TB}{\Delta Q}$

Example: If producing a third widget increases total cost from $100 to $120, the marginal cost of the third widget is $20.

Macroeconomics vs Microeconomics

Economics is divided into two main branches: microeconomics and macroeconomics.

• Microeconomics: Studies individual agents (consumers, firms) and markets.

• Macroeconomics: Examines the economy as a whole, including aggregate indicators like GDP, inflation, and unemployment.

Example: Microeconomics analyzes how a firm sets prices; macroeconomics studies national unemployment rates.

Normative vs Positive Statements

Economic statements can be classified as either positive or normative.

• Positive Statements: Objective and fact-based; describe what is.

• Normative Statements: Subjective and value-based; prescribe what ought to be.

Example: "Increasing the minimum wage will reduce employment" (positive); "The government should increase the minimum wage" (normative).

Production Possibility Frontier (PPF)

The PPF illustrates the maximum feasible combinations of two goods that an economy can produce, given available resources and technology.

• Shape: Typically bowed outward due to increasing opportunity costs.

• Points on the PPF: Efficient (on the curve), inefficient (inside the curve), and unattainable (outside the curve).

Formula:

• $Opportunity\ Cost = \frac{Loss\ of\ Good\ Y}{Gain\ of\ Good\ X}$

Example: If moving from point A to B on the PPF means producing 10 fewer cars to produce 5 more computers, the opportunity cost of each computer is 2 cars.

Comparative vs Absolute Advantage

These concepts explain how individuals or countries benefit from specialization and trade.

• Absolute Advantage: The ability to produce more of a good with the same resources than another producer.

• Comparative Advantage: The ability to produce a good at a lower opportunity cost than another producer.

Example: If Country A can produce both wheat and cloth more efficiently than Country B, it has an absolute advantage. If Country A sacrifices less cloth to produce wheat than Country B, it has a comparative advantage in wheat.

Specialization and Terms of Trade

Specialization occurs when economic agents focus on producing goods for which they have a comparative advantage. Terms of trade determine the rate at which goods are exchanged between agents.

• Terms of Trade: The agreed-upon rate of exchange of goods between two parties.

• Benefit: Both parties can consume beyond their individual PPFs through trade.

Example: If two countries specialize and trade, both can achieve higher consumption levels than without trade.

Demand and Supply Shifters

Various factors can shift the demand and supply curves, affecting equilibrium price and quantity.

• Demand Shifters: Income, tastes, prices of related goods, expectations, number of buyers.

• Supply Shifters: Input prices, technology, expectations, number of sellers.

• Shifts vs Movements: A shift refers to a change in the entire curve; a movement refers to a change along the curve due to price changes.

Example: An increase in consumer income shifts the demand curve for normal goods to the right.

Elasticities

Elasticity measures the responsiveness of quantity demanded or supplied to changes in price or other factors.

• Price Elasticity of Demand: $E_d = \frac{\%\ \text{change in quantity demanded}}{\%\ \text{change in price}}$

• Income Elasticity of Demand: $E_I = \frac{\%\ \text{change in quantity demanded}}{\%\ \text{change in income}}$

• Cross-Price Elasticity of Demand: $E_{xy} = \frac{\%\ \text{change in quantity demanded of good X}}{\%\ \text{change in price of good Y}}$

Example: If a 10% increase in price leads to a 20% decrease in quantity demanded, the price elasticity of demand is -2.

Essential Computations in Microeconomics

Opportunity Costs in Production

Opportunity cost is the value of the next best alternative foregone when making a decision.

• Calculation: Compare the loss of one good to the gain of another when resources are reallocated.

Formula:

• $Opportunity\ Cost = \frac{Loss\ of\ Good\ Y}{Gain\ of\ Good\ X}$

Equilibrium Price and Quantity

Market equilibrium occurs where quantity demanded equals quantity supplied.

• Equilibrium Price ($P^*$): The price at which the market clears.

• Equilibrium Quantity ($Q^*$): The quantity bought and sold at equilibrium price.

Formula:

• Set $Q_d = Q_s$ and solve for $P^*$ and $Q^*$.

Example: If $Q_d = 100 - 2P$ and $Q_s = 20 + 3P$, set $100 - 2P = 20 + 3P$ to solve for $P^*$.

Surplus and Shortage Magnitude

Surplus and shortage occur when the market is not in equilibrium.

• Surplus: Quantity supplied exceeds quantity demanded at a given price.

• Shortage: Quantity demanded exceeds quantity supplied at a given price.

• Magnitude: $|Q_s - Q_d|$ at the non-equilibrium price.

Example: At $P = 10$, if $Q_s = 60$ and $Q_d = 40$, there is a surplus of 20 units.

Market Supply and Demand from Individual Curves

Market supply and demand are the sum of individual supply and demand curves.

• Market Demand: Sum of all individual quantities demanded at each price.

• Market Supply: Sum of all individual quantities supplied at each price.

Example: If two consumers demand 10 and 15 units at $P = 5$, market demand is 25 units at that price.

Elasticities Computation

Elasticity calculations help determine how sensitive quantity is to changes in price, income, or other goods' prices.

• Price Elasticity of Demand: $E_d = \frac{\Delta Q / Q}{\Delta P / P}$

• Income Elasticity of Demand: $E_I = \frac{\Delta Q / Q}{\Delta I / I}$

• Cross-Price Elasticity: $E_{xy} = \frac{\Delta Q_x / Q_x}{\Delta P_y / P_y}$

Example: If quantity demanded increases by 5% when income rises by 10%, income elasticity is 0.5.